Question

In diborane ($\text{B}_2\text{H}_6$), the number of bridge hydrogens is

• A. 2
• B. 4
• C. 6
• D. 0

Hint:

Remember that in $\text{B}_2\text{H}_6$, the two hydrogen atoms that are bonded to both boron atoms act as bridge hydrogens.

Answer 1

The Correct Option is A

Step 1: Concept
In organic and inorganic compounds, hydrogen atoms can bond directly to a central atom or bridge between two different central atoms. In the context of $\text{B}_2\text{H}_6$, we need to understand how boron and hydrogen are bonded to determine the number of bridge hydrogens.

Step 2: Meaning
Bridge hydrogen refers to a hydrogen atom that is bonded to two different boron atoms in a molecule like diborane. In $\text{B}_2\text{H}_6$, each boron atom has three valence electrons, and it forms three single bonds with hydrogen atoms or one bond with another boron atom.

Step 3: Analysis
Diborane ($\text{B}_2\text{H}_6$) consists of two boron atoms bonded to six hydrogen atoms. The structure can be visualized as a linear chain where each boron atom forms three single bonds, and these bonds are shared between the boron atoms and hydrogen atoms. Boron has 3 valence electrons. Each bond formed by boron with another boron or a hydrogen uses one of its valence electrons. Therefore, in $\text{B}_2\text{H}_6$, each boron atom forms three single bonds: two with hydrogen and one with the other boron. This means that out of the six hydrogen atoms, four are bonded directly to only one boron atom (terminal hydrogens), while two hydrogen atoms act as bridge hydrogens, bonding to both boron atoms. This configuration ensures that each boron atom has a complete octet or duet, satisfying the octet rule for boron.

Step 4: Conclusion
The number of bridge hydrogens in diborane ($\text{B}_2\text{H}_6$) is 2. Final Answer: (A)